A direct torque controlled cage induction generator using back to back PWM converters for grid connected variable speed wind energy system

A wind energy conversion system (WECS) differs from a conventional power system in a lot of ways. In a conventional power plant, the power generation can be controlled easily, as the fluctuations in active and reactive power are not so frequent. But, the power output of a WECS fluctuates with the wind velocity, which makes it difficult to analyze and control. Various approaches have been developed to enhance the performance of a WECS. A variable-speed wind turbine has two back-to-back PWM converters which consists of a machine-side converter for generator control and a grid-side converter for grid-side power control. In this paper Direct Torque Control scheme has been adopted for generator- side convertor control and Grid voltage oriented Vector control scheme is adopted for controlling the grid- side convertor. In both the schemes PI controllers are used. The whole scheme is simulated in Matlab and the results are interpreted.